In wireless communication systems, a radio access network generally comprises one or more access nodes (such as a base station) which communicate on radio channels over a radio or air interface with plural wireless terminals. In some technologies such a wireless terminal is also called a User Equipment (UE). A group known as the 3rd Generation Partnership Project (“3GPP”) has undertaken to define globally applicable technical specifications and technical reports for present and future generation wireless communication systems. The 3GPP Long Term Evolution (“LTE”) and 3GPP LTE Advanced (LTE-A) are projects to improve an earlier Universal Mobile Telecommunications System (“UMTS”) mobile phone or device standard in a manner to cope with future requirements.
In typical cellular mobile communication systems, the base station broadcasts on the radio channels certain information which is required for mobile stations to access to the network. In Long-Term Evolution (LTE) and LTE Advanced (LTE-A), such information is called “system information” (“SI”). Each access node, such as an evolved NodeB (“eNB”), broadcasts such system information to its coverage area via several System Information Blocks (SIBs) on downlink radio resources allocated to the access node.
In RAN#71, the study item (SI) “Further Enhancements LTE Device to Device, UE to Network Relays for IoT and Wearables” (also called Further enhanced D2D (FeD2D)) was agreed. See, e.g., RP-160677, “New SI: Further Enhancements LTE Device-to-Device, UE-to-Network Relays for Wearables”, Qualcomm Incorporated, Intel Corporation, Huawei, HiSilicon, LG Electronics Inc., Gothenburg, Sweden, Mar. 7-10, 2016, incorporated herein by reference. The main focus of this SI is to address the issue of power efficiency for evolved remote UEs (e.g., Internet of Things (IoT)), such as machine type communication (MTC) [See, e.g., 3GPP TR 36.888, V12.0.0, “Study on provision of low-cost Machine-Type Communications (MTC) User Equipments (UEs) based on LTE, incorporated herein by reference] or narrowband (NB-IoT), or wearable devices).
To achieve this goal, the following objectives were proposed:                study and evaluate a generic Layer 2 evolved UE-to-Network Relay (eUTNR) architecture, including methods for the network to identify, address, and reach an evolved Remote UE via an evolved ProSe UE-to-Network Relay (UTNR) UE:        Study the possibility of a common solution supporting the following use cases:                    a. UE to network relaying over non-3GPP access (Bluetooth/WiFi).            b. UE to network relaying over LTE sidelink.            c. Unidirectional and bidirectional UE to network relay.                        
In order to make further progress in this study, the following coverage scenarios were agreed in RAN#72 [See, e.g., RP-161303, Further Enhancements to LTE Device to Device, UE to Network Relays for IoT and Wearables, RAN#72, Korea, June 2016, incorporated herein by reference]:                Evolved Remote UE and evolved ProSe UE-to-Network Relay UE are EUTRAN incoverage.        Evolved ProSe UE-to-Network Relay UE has a Uu connection to the eNB and evolved Remote UE can be in enhanced coverage. “Enhanced coverage” implies that the UE is connecting to the network via NB-IOT or Rel-13 MTC in CE mode.        Evolved ProSe UE-to-Network Relay UE is in EUTRAN coverage and evolved Remote UE is out of coverage of EUTRAN.        
Relay nodes (RN) play important roles in LTE Rel-13 device to device (D2D) communications, as it can help extend network coverage. In FeD2D, 3GPP RAN2 is studying enhancements on UE-to-Network relay to support commercial use cases, e.g. IoT and wearable devices, etc. One aspect being considered is the QoS support of the UE-to-Network relay over LTE sidelink. Another aspect is generic Layer 2 evolved UE-to-Network Relay architecture study, instead of Layer 3 UTNR in Rel-13, so as to let network be able to control and charge the evolved remote UEs. Another aspect is for evolved remote UE energy saving, especially for NB-IoT and MTC UEs in their enhanced coverage, large amount of repetitions have to be done in order to maintain the coverage, which not only waste lots of spectrum resources, but also consumes lots of power for evolved remote UEs. Transmission via Evolved UTNR can help deep coverage evolved remote UE save power, and out of coverage evolved remote UE being able to connect to the network.
Both user plane (UP) and control plane (CP) can be relayed through evolved UTNR. Reading the broadcast information (e.g. system information) over Uu interface seems to be burdensome to the UE if many repetitions of the UEs are required to read those broadcast information. In the current 3GPP, very few simple and high level discussions were made on this topic. The question has been raised that, since relay UE does not know the category of the remote UE, the relay UE does not know which system information blocks are necessary for remote UE. See, e.g., R2-165599, “Relaying options of CP/UP”, LG Electronics Inc., Gothenburg, Sweden, Aug. 22-26, 2016, incorporated herein by reference. Thus, with respect to a remote UE, “it needs to be evaluated whether the benefit of reception of many repetitions is comparable to unnecessary SIB reception”.
In addressing problems posed above and particularly issues regarding system information, it must be remembered that, while the evolved UTNR should always be in coverage, the evolved remote UE can be in coverage, or in enhanced coverage, or out of coverage, with each of these differing scenarios having different issues in terms of both power consumption and in the evolved UE reading system information.
What is needed, therefore, and an example object of the technology disclosed herein, are methods, apparatus, and techniques for enabling a remote UE/evolved remote UE to obtain system information.